In the past, various different types of past or prior art control devices, such as fluid pressure actuated switches for instance, were utilized in an automotive type air conditioning system to control the energization and deenergization of a clutch actuated compressor in the system in response to a preselected low and high value of fluid pressure measured at a preselected point in the system, such as for instance in an accumulator or the like in the system. One such past control device is disclosed in the copending Ronald W. Poling application Ser. No. 960,172 filed Nov. 13, 1978, (now U.S. Pat. No. 4,200,776 issued Apr. 29, 1980) which is incorporated herein by reference.
These past control devices were provided with a housing having an opening therethrough, and a movable fluid pressure responsive member, such as a diaphragm or the like for instance, was sealably interposed across the opening in the control device housing so as to define therein a pressure fluid chamber and a switch means accommodating chamber adjacent the opposite sides of the diaphragm, respectively. A snap-action member movable between a stable configuration and an unstable configuration thereof was provided with a circumferential edge seated in the switch means accommodating chamber on the control device housing generally about the opening therein and adjacent the diaphragm, and a switching means operable generally between make and break positions for controlling a circuit through the control device was disposed in the switch means accommodating chamber generally adjacent the snap-action member. Thus, the diaphragm was movable in response to a preselected fluid pressure acting thereon in the pressure fluid chamber to effect the application of a motive or applied force onto the snap-action member thereby to cause a snap-action movement of the snap-action member from the stable configuration toward the generally inverted or unstable configuration thereof. When the snap-action member was so moved to its unstable configuration, it effected the movement of the switching means between its break position to its make position. Thereafter, in response to a reduction of the fluid pressure in the pressure fluid chamber and a corresponding reduction in the motive force acting on the snap-action member, the snap-action member returned with snap-action from its unstable configuration to its stable configuration thereby to permit return movement of the switch means from its make position to its break position. Of course, in its make and break positions, the switch means completed and interrupted the circuit through the control device which effected the energization and deenergization of the aforementioned clutch controlled or actuated compressor, respectively.
In at least some of these past control devices, an actuator was associated with a resilient current carrying arm of the switching means, and a post integral with the actuator was disposed to engage with the snap-action member substantially at a center point of a central portion thereof. Of course, when the snap-action member was actuated to its unstable configuration in response to the motive force acting thereon, as discussed above, the center point of the snap-action member engaged with the post of the actuator effected conjoint movement of the actuator with the snap-action member in order to move the arm of the switching means into the aforementioned make position thereof completing the circuit through the control device. It is believed that one of disadvantageous or undesirable features of the aforementioned at least some past control devices was that the repeated engagement or pounding of the actuator post against the highly stressed center point of the snap-action member may have added enough stress thereto to cause fracturing of the snap-action member. The repeated engagement or pounding of the actuator post against the center point of the snap-action member is believed to have been caused by undulations in the arm of the switching means which is effected by the inability of such arm to follow in engagement with the snap-action member as it translates very rapidly between the stable configuration and the unstable configuration thereof.
In others of the aforementioned past control devices, a range or coil spring had the opposite ends thereof respectively biased into engagement between a retainer therefor on the actuator and an adjusting screw threadably received in the housing of the past control devices. Of course, the range spring was utilized to adjust the forces respectively necessary to cause the snap-action movement of the snap-action member between its stable and unstable configuration. However, if the opposite end faces of the range spring and the complementary seating surfaces therefor on the actuator retainer and/or the adjusting screw were not absolutely square with each other, i.e., such opposite end faces and/or seating surfaces had tolerance variations, the range spring may have been side loaded in order to nest the opposite ends of the range spring on the seating surfaces therefor of the actuator retainer and the adjusting screw, respectively. Due to this side loading effect of the range spring, the compressive force thereof may have been so misaligned or otherwise misdirected as to cause tipping or tilting of the actuator post in its engagement with the center point of the snap-action member. It is believed that a disadvantageous or undesirable feature associated with the aforementioned tipping of the actuator post in its engagement with the snap-action member was that the effective length of the post may have been changed enough to result in the distortion of the switching means arm so as to alter the preselected switching characteristics thereof. In this vien, an analogous disadvantageous or undesirable feature is believed to be that aforementioned change in the effective length of the actuator post due to the tipping thereof may have also displaced the contact opening and closing positions of the switching means arm from those preselected therefor. In other words, with the contact opening and closing positions of the switching means arm so altered, the preselected stroke or displacement of the snap-action member upon its movement between the stable and unstable configurations thereof may not be enough to move the switching means arm into its contact closing position or, in the alternative, may have been too much so as to prevent the movement of the switching means arm to its contact opening position. This condition might, of course, have caused the switching means to either creep open or to close before the snap-action member snaps into its unstable configuration.